Balanced pneumatic suspensions including an automatic level control



M DANGAUTHIER VIATIC SUSPENSIONS INCLUDING AN AUTOMATIC LEVEL CONTROL Nov. 10, 1964 BALANCED PNEU:

Filed March 26, 1962 2 Sheets-Sheet 1 Marcel Da INVENTOR autlu'er A T TORNEYS 1964 M. DANGAUTHIER BALANCED PNEUMATIC SUSPENSIONS mcwoxuc AN AUTOMATIC LEVEL CONTROL Filed March 26, 1962 2 Sheets-Sheet 2 Fig.4

[Ni ENI'OR M areal Duyazu k ier United States Patent 3,156,481 llALANfIED PNEUh iATi SUSPENSEIONS INCLUD- lNG AN AUTQMATEQ LEVEL GNTRGL Marcel Dangauthier, Paris, France, assigner to Societe dEtudes et dApplications lndustrieiles Commereiales et lmmobiiieres inter-Technique, Paris, France, a French body corporate Filed Mar. 26, 1962, Ser. No. 182,443 (Claims priority, application France, Apr. 4, 1961, 857,675, Patent 1,293,578 5' Claims. (Cl. zen-e The invention relates to balanced pneumatic suspensions including an automatic level control, or control of the ground clearance of the suspended mass.

Pneumatic suspensions of this type have been known for a long time; the balancing-adapted to prevent inclination of the suspended mass under the effect of an unequal distribution of the load, of a slope in the road or of the centrifugal force when travelling round a bend-is achieved by providing intercommunication so as to balance the pressures between the springs or pneumatic supporting elements of the same set or pair of wheels and be connected by means of an anti-roll torsion bar the pistons of said springs or pneumatic supporting elements. An arrangement of this type is for example described in the French Patent No. 637,592 to Messier, filed November 9, 1926. The automatic level control is achieved by the piston of the pneumatic spring which, at the end of its reciprocations, causes admission of compressed air in the cylinder or its discharge to the exterior air.

This automatic level control by purely pneumatic means has various practical drawbacks; hydraulic means of two types have been proposed to overcome these drawbacks.

in the first method, the cylinder of the pneumatic supporting elements has connected thereto a pipe which, through the medium of a damped level corrector under the control of the up and down movements of the wheel or of the mid-point of the axle, is put in communication either with a liquid reservoir communicating with the exterior air or with a hydraulic presure accumulator so as to supply or discharge liquid as a function of the height at which the suspended part would tend to become stabilized when the vehicle is stationary, if no level corrector existed. t

In the second method, the cylinder of the pneumatic supporting element has connected thereto at two different levels: a pipe in constant communication with the outlet of a continously operating liquid pump and a pipe in intermittent communncation with a liquid reservoir com municating with the exterior air, said intermittent communication being controlled by the piston of the supporting element itself, thereby providing not a level correction but its automatic maintenance without any additional means or distributor.

It is said second method which is employed in the system of the pneumatic suspension according to the invention.

In the prior U.S. Patent No. 3,088,726 of May 7, 1963, there is described an advantageous arrangment of a supporting element of utility in the pneumatic suspension of the aforementioned second type, in which the circulation of the liquid serving to automatically control the level or ground clearance of the suspended part also serves to damp the suspension by constraining the liquid to pass through spring-pressed valves having a calibrated spring in accordance with a known principle.

The object of the present invention is to provide a pneumatic suspension assembly which employs supporting elements which are of the type described in the aforesaid U.S. patent and some of which are modified to take into account considerations of position or size or to permit their adaptation to steering wheels and in which the balancing of the suspended mass is improved relative to the balanced suspension disclosed by the aforementioned French patent to Messier.

Although it is a current practice to name the type of suspension described hereinafter a hydro-pneumatic or oleo-pneumatic suspension, this terminology leads to confusion since the hydraulic part of the suspension is constituted by an incompressible fluid which is therefore incapable of offering an elastic resistance to the movements or oscillations of the wheels, and it is incorrect to attribute thereto, even partially, a function in the suspension, its function being exclusively that of an intermediate or transmission element permitting an easy achievement of fluid tightness and avoiding losses of compressed gas, and possibly that of a retarding or damping element in the course of its iiow through orifices or valves. This is why it has been decided to term the suspension described hereinafter as a pneumatic suspension provided with an automatic level control and a damping by hydraulic means.

The balancing method already proposed for pneumatic suspension referred to hereinbefore in which the pressures in the supporting elements are balanced by putting the latter in permanent communication with one another and in which the pistons are connected to an anti-roll bar, presents operational difficulties. The torsional reaction force necessary to overcome the disturbing torque which tends to incline the body or frame of the vehicle is of large magnitude and requires a torsion bar of rather large diameter and this increases in an undesirable manner the weight of the unsuspended mass and of the transmission means transmitting this reaction force. Further, the inclination of the suspended mass does not have a precise limit since the reaction force increases in proportion to the inclination. The applicant has found that it is possible to substitute, at least partially, a purely hydraulic automatic reaction device for the anti-roll torsion bar and thus relieve the latter of some of its work and permit a lighter torsion bar, the latter intervening in the suspension system in respect of the small transverse inclinations of the suspended mass and the hydraulic reaction device in respect of an inclination which reaches a certain value limited by the hydraulic anti-tilt device.

To this end, in the conduit which puts the pneumatic supporting elements in communication with one another and permanently connects the latter to the outlet of the pump, the latter being necessarily a volumetric pump, there is provided, on both sides of the branch conduit connected to the pump, a calibrated orifice adapted to create a large increase in the static pressure of the liquid on the side of the depressed supporting element when the latter is temporarily isolated from the reservoir communicating with the exterior air, this pressure increase occurring above the calibrated orifice (with respect to the flow) which at this moment must allow through an increased liquid flow to the opposite supporting element, andcreating the necessary additional reaction torque to return the suspended mass to the horizontal position.

Another important feature of the invention resides in the construction of an independent suspension for the steering wheels of the vehicle which also has the features described hereinbefore but is so arranged as to take into account exacting considerations of location and size.

Further features and advantages of the invention will be apparent from the ensuing description, with reference to the accompanying drawings, to which the invention is in no way limited.

In the drawings:

FIG. 1 is a perspective assembly diagram of the suspension, some of the supporting elements being shown in section;

FIG. 2 is a sectional view on an enlarged scale of the hydraulic anti-tilt device;

FIG. 3 is a vertical sectional view of the supporting element of a steering Wheel and of the device associated therewith, and

FIG. 4 is a partial sectional view on an enlarged scale of the supporting element shown in FIG. 3.

With reference to FIG. 1, the suspension according to the invention has a number of pneumatic suspension supporting elements A, A, B, B, the elements A, A being associated with the steering wheels such as R and the elements B, B with the non-steering wheels, for example the driving wheels R.

The supporting elements comprise a chamber 1 for the elements A, A, a chamber 2 for the elements B, B which contain a cushion of air under pressure, the pressure of this air cushion being transmitted to a piston 3 for the elements A, A, and the piston 4 for the elements B, B. In order to stabilize the ground clearance or level of the suspended mass under good conditions, as to fluid tightness, permit the hydraulic damping of the suspension and contribute to the transverse stability of the suspended mass, a liquid such as oil is employed between the air cushion and the pistons in the cylinders 5 (elements A, A) and 6 (elements B, B) in which move the respective pistons 3 and 4, and the supporting elements A and A are interconnected by an intercommunication conduit and the supporting elements B and B are interconnected by an intercommunication conduit 8.

The cylinders of the supporting elements are connected to the suspended mass of the vehicle and their pistons are connected to the unsuspended mass. In the presentlydescribed embodiment, the cylinders 6 of the elements B, B are connected to the suspended mass, symbolized by a vehicle body or shell 9, and their pistons 4 to an axle, for example the rear axle 10 of the vehicle. The cylinders 5 of the elements A, A are connected to the unsuspended mass for example the stub axles 11 of the wheels R and their pistons 3 are connected to the suspended mass symbolized by an element of the vehicle body or shell 12.

It will be understood that the movements or oscillations of the wheels while the vehicle is travelling result in alternating movements on the part of the pistons 3, 4 in the cylinders 5, 6 and this creates an elastic compression or expansion of the air in the air cushions 1 and 2 constituting the pneumatic suspension.

The pistons 4 of the elements B, B are interconnected by an anti-roll torsion bar 13 whose transverse portion is journalled in bearings 14 connected to the suspended mass 9 and whose longitudinal arms 15 are connected by links 16 to the ends of the axle it connected to these pistons. Similarly, the cylinders 5 are interconnected, through the medium of elements which will be described hereinafter, by an anti-roll torsion bar 17 whose transverse portion is journalled in bearings 18 connected to the suspended mass 12 and Whose longitudinal arms 19 are connected to the cylinders 5. If desired, these torsion bars could be replaced by any other known equivalent devices.

The intercommunications conduits 7 and 8 and the anti-roll bars 13 and 1'7 contribute toward the transverse balance or equilibrium of the pneumatic suspension in accordance with the principle disclosed in said French patent to Messier, namely that if one of the cylinders undergoes with respect to its piston a certain relative displacement different from that undergone by the other cylinder with respect to its piston of the same set of wheelswhich tends to incline the suspended mass to one side or the otherthe elastic torsion of the anti-roll bar tends to reestablish the equilibrium, the pressures of the corresponding air cushions being balanced by the conduits 7 or 8, at any rate in the first operational stage.

The automatic level control is realized in accordance with the known method of introducing in the cylinders 5 and 6 a liquid separated from the air cushions 1 and 2 by a movable or deformable separator such as a diaphragm 1a, 2a, and connecting to the cylinders 5 or 6 of each pneumatic supporting element at two different levels of the space containing the liquid, a conduit in constant communication with the outlet of a continuously operating liquid pump 20 and a conduit in intermittent communication with a reservoir of liquid communicating with the exterior air, such as 21, this intermittent communication being controlled by the piston 3 or 4 of the supporting elements A, A or B, B itself, which insures an automatic control of the level as disclosed in said US. patent.

As mentioned in the latter, advantage is taken of the presence of the liquid permitting the automatic control of the level to damp the suspension by a lamination of the liquid through calibrated spring-loaded valves acting in both directions. These well-known liquid lamination elements are designated generally by the reference numeral 22 in respect of the elements A, A and 23 in respect of the elements B, B.

An important feature of the invention resides in the fact of utilizing the displacements of the liquid between the pump and the cylinders of the supporting elements to create an automatic return etfect of the suspended mass in the case of a tilt of large magnitude, the anti-roll bars participating in this function only in respect of a roll of small amplitude.

This additional function of the liquid requires a more detailed description of the supporting elements and of their connection to the pump it and to the low-pressure reservoir 21.

Referring firstly to the supporting elements B, B the lower connections 24 of the cylinders 6 opening out in front of calibrated orifices 24a in the Wall of the cylinder are interconnected by a conduit 25 connected to a common conduit 26 which is in turn connected to a collector conduit 27 leading to the low-pressure reservoir 21. The upper connections 28 of the cylinders 6 are interconnected by the intercommunication conduit 8 connected to a common conduit 29 in turn connected to a collector conduit 30 leading to the delivery side of the pump 20.

As concerns the supporting elements A, A, the lower connections 31 of the cylinders 5 are interconnected by a conduit 32 connected to a common conduit 33 in turn connected to the low-pressure collector conduit 27. The upper connections 34 of the cylinders 5 are interconnected by the intercommunication conduit 7 which is connected to a common conduit 35 itself connected to the highpressure collector conduit 30.

The connections 28 of the supporting elements B, B communicate with the annular compartment 6 of the cylinder 6 which is separated from the latter by a sleeve 36, this sleeve being isolated at its base from said cylinder by a sealing joint 37 and communicating at its upper part with said cylinder by Way of the valved orifices pertaining to the hydraulic damper 23 which permit the flow of the liquid to the air cushions 2 through a large orifice 38 whereas the flow of the liquid in the opposite direction through the orifice 38 is damped by the valved orifices of the hydraulic damper 23 which allow this reverse flow. The springs of the valves are calibrated in such manner as to provide a selective damping of the flow of the liquid in both directions in the known manher.

The intercommunication conduit 8 is connected to the common conduit 29 through the medium of a stop-valve housing 39 the valve 40 of which permits the flow of the liquid from the conduit 29 to the two branches of the conduit 8 but prevents the flow of the liquid in the opposite direction.

A practical embodiment of this valve will be described hereinafter with reference to FIG. 2.

Disposed on both sides of the valve housing are two calibrated orifices or restricted passageways 41, 42 in the form of apertured diaphragms the anti-tilt effect of which will be explained hereinafter.

FIG. 2 shows a practical embodiment of this arrangement in which the diaphragm jets 41, 42 and the valve 40 are combined in a single unit in the form of a T- shaped coupling.

The body 39a of the unidirectional or stop valve 46 has three communicating bores; one of .these bores is provided with the valve 40 constituted by an annular sealing element of rubber surrounding a cylindrical rod 44 and held in position by a pipe coupling screw 45. The annular part of the valve 40 is capable of moving away from the rod 44 when the liquid enters in the direction of arrow F and issues from the body 39a in the directions of arrows F and F but the liquid pressure presses it back against the rod 44 when the liquid flows in the opposite direction. The other two bores, which are perpendicular to the first-mentioned bore, comprise apertured diaphragms 41, 42 constituted by washers which have calibrated orifices 45, 46 and are maintained in position by pipe coupling screws 47, 48.

The screws 47, 48 couple the body 39a to the two portions of the conduit 8 and the coupling screw 45 couples this housing to the conduit 29.

The arrangement is similar as concerns the supporting elements A, A, except that it is necessary to take into account the space available for these elements and their adaptation to the steering wheels. As mentioned hereinbefore, the connection of the supporting elements A, A to the suspended and unsuspended masses of the vehicle is reversed with respect to that of the supporting elements B, B. In the presently-described embodiment, the chamber containing the air cushion 1 is disposed the other way round to the chamber containing the air cushion 2 so that it is surmounted by the damper 22 and the piston 3 extends into the cylinder through the upper end of the latter. Whereas the piston 4- of the elements B, B is preferably closed at its upper part by a disc 4% in order to reduce the amount of oil stored in the elements 13, B the piston 3 of the elements A, A is constituted by a hollow plunger which is open at its lower part and which, in moving with respect to the orifice 5'9 of a jet 51 mounted in a sleeve 52 constituting a part of the wall of the cylinder, controls the intermittent communication between the cylinder and the low-pressure reservoir.

In the course of the movements or oscillations of the wheels connected to the supporting elements B, B the pistons 4 of the latter mask and unmask the orifices 24a communicating with the low pressure.

If the mean position of the piston 4 is on a level with the orifice 24a, the amount of liquid pumped by the volumetric pump 20 exactly compensates the escape of liquid by way of the conduit 25 and the pressure of the air cushion remains constant.

If the mean position of the piston 4 tends to rise owing to an increased load on the suspended mass causing the piston 4 to move further into the cylinder 6, the flow of the liquid delivered by the pump exceeds the intermittent escape by way of the orifice 24a and the liquid discharged through the connection 28 urges the piston outwardly of the cylinder. The level or ground clearance is automatically re-established and the pressure of the air cushion 2 is increased so as to balance the heavier load.

If the mean position of the piston 4 tends to descend owing to a diminished load on the suspended mass causing the piston 4 to move outwardly of the cylinder 6, the flow of the liquid by way of the orifice 24a exceeds the flow of the liquid through the apertured diaphragm 41 and the piston moves once more inwardly of the 6 cylinder and the level or ground clearance is re-established automatically.

Further, the drop in the pressure in the cylinder caused by the uncovering of the orifice 24a reduces the pressure in the supporting element and the air in the cushion 2 expands.

The foregoing description of the operation concerns one ofthe supporting elements B, B considered alone.

If the two supporting elements of the same set of wheels are now considered, and if one of them (for example B) is loaded more than the other (B'), the suspended mass tends to become transversely inclined. The conduit 8 initially performs its function of balancing the pressures between the two air cushions 2 whereas the anti-roll bar 13 intervenes owing to its torsional elasticityto reestablish the equilibrium by exerting a torque which tends to draw the piston 4 outwardly of the cylinder 6 of the element B and to push the piston 4 inwardly of the cylinder 6 of the element B.

So long as the lack of equilibrium is manifested by moderate difierences in the elongations of the pistons and their cylinders, the torsion bar is sufiicient in re-establishing the equilibrium, its elastic reaction being proportional to the angle of torsion. It will be observed that in this situation the pressure is equal in the two air cushions of the same set of wheels as occurs in the Messier arrangement mentioned hereinbefore.

But if the outside forces exerted on the suspended mass are such that the diiference in the elongation of the pistons and their cylinders increases, the reaction force of the torsion bar 13 is no longer sufilcient to re-establish the equilibrium (unless its rigidity, namely its section and weight, is increased to a value which would adversely affeet the road holding qualities of the vehicle) and it is then that the anti-tilt effect of the apertured diaphragms 41, 42 come into action.

Assuming, for the sake of simplication, that the vehicle is in a state of rest, if the lack of equilibrium is such that the orifice 24a of the element B is closed and the orifice 24a of the element B uncovered, the flow of liquid through the diaphragm 41 becomes nil and the element B, being no longer supplied with liquid, tends to sink. The volumetric pump 2% thenceforth pumps solely through the apertured diaphragm 42 the fiow through which is suddenly doubled. Consequently, there is an increase in the pressure on the upstream side of the diaphragm 42 with respect to the direction of flow which is transmitted statically through the diaphragm 41 to the cylinder 6 and to the air cushion 2. (The pressure is increased about four times since it is roughly proportional to the square of the flow.) This sudden increase in pressure creates a powerful reaction effect which is added to that of the anti-roll bar and limits the tilt to a maximum value.

Tests carried out with a vehicle equipped at the rear with pneumatic supporting elements B, B and diaphragms 41, 42, an anti-roll bar 13 and dampers 23, have demonstrated that it is possible to obtain in a stabilized turn a reaction torque of about 210 mkg. when unloaded and 24-0 mkg. when loaded, the action of the diaphragms intervening in these figures to the extent of about mkg. (taking into account the cross-section of the pistons and the supporting elements).

These results were obtained with diaphragm orifices having a diameter of 1.25 mm. and a liquid flow of 1000 cmfi/min, the pressure drop through the diaphragm orifices being 20 kg./cm.

The operation in respect of the supporting elements A, A is similar.

In the course of the movements or oscillations of the steering wheels A, A, the piston 3 of the latter masks and unmasks the orifices 50 which communicate with the low pressure and whose full flow is equal to the flow of the liquid pumped through the connection 34.

If the mean position of the piston 3 is located on a level with the orifice 5%) there is a compensation between 6 the liquid supplied by the pump and the liquid escape to the low pressure and the pressure of the air cushion remains constant.

in the event of lack of equilibrium, the operation is the same as that described in respect of the elements B, B except that the sliding of the piston 3 inwardly of the cylinder 5 results from a rising of the cylinder 5 and viceversa.

To obtain a transverse balance or equilibrium there are associated with the torsion bar 17 and with the intercommunication conduit 7 apertured diaphragms 41 and 42 similar to the aforementioned diaphragms and there is also provided a unidirectional or stop valve 4%) so as to maintain the pressure in the system during the periods in which the pump is inoperative.

The volumetric pump 2t can be of any known type and, if desired, in the form of a pair of pumps, one pump being supplied for each axle. When there is only a single pump it is necessary to provide at the branch connection of the conduits 3t}, 29 and a How distributor atia so as to distribute the entire flow from the volumetric pump in a given fixed ratio between the forward and rear supporting elements of the vehicle irrespective of their operational pressure, this ratio being determined by the differences in the conditions of operation of these supporting elements and in particular when braking. This flow distributor can be of any known commercially available type. The pump can be controlled by a camshaft 54, for example driven by the motor of the vehicle, the cam of which actuates the driving element 56 of the pump.

In order to regularize the output of the pump and avoid hammering in the conduits, the pump is preferably associated, as are most volumetric pumps, with an antihammer chamber 57 having an air cushion 55 of small capacity. For example, this chamber could have a capacity of 50 cm. (in comparison, the capacity of the chamber of each of the supporting elements enclosing an air cushion 1 or 2 would be about 1000 cmfi).

In order to insure that there is no excessive rise in pressure the outlet and inlet sides of the pump could be interconnected by a by-pass conduit 59 in which is inserted a safety valve 60. The inlet pipe of the pump 20 advantageously includes an apertured diaphragm 2% which restricts the delivery of the pump to a maximum irrespective of the operational speed.

It will be observed that the stop valves 4i) tend to maintain the pressure on the downstream side in the supporting elements but that the seal obtained by the masking of the orifices 24a and 50 by the pistons 4 and 3 is not perfect owing to the necessary operational clearances, so that if the vehicle is stationary with the pump stopped during several hours leakage of liquid occurs, the pressure tends to drop and the suspended mass tends to sink.

This sinking is restricted by the toroidal sealing rings or the like 61 and 62 disposed in such manner as to pro ject from the wall of the cylinders of the elements A, A and B, B a little beyond the orifices 59 and 24a in the direction in which the pistons move into the cylinders, said pistons abutting against these rings in a perfectly iluidtight manner for a slight sinking of the suspended mass. This slight sinking is taken up or compensated for in a few seconds as soon as the pump has been started up, since the volume of liquid necessary is very small. The mounting of the sealing rings 62 of the elements B, B is effected as described in said US. Patent No. 3,088,726. The mounting of the sealing rings 61 will be described hereinafter.

The mounting of the supporting elements B, B in respect of wheels which are not steering wheels presents no particular problem. It is achieved preferably with interposition between the cylinder 6 and the vehicle body 9 of a rubber joint 63 and between the piston 4 and the axle 10 of a rubber joint 64.

With respect to the steering wheels R, namely usually the front wheels, the construction of the supporting elements A, A must take into account the particular conditions of position and operation of these elements.

First, as the stub axles 11 are connected to the supporting elements, the orientation or locking of the wheels must be possible in the usual manner by means of steering arms such as 65 fixed in bosses 66 which are rigid with the axles 11 as concerns rotation. These elements must furthermore be connected to the suspended mass by a kinematic linkage so that the movements or oscillations of the wheels conform to the usual law or requirements in steering design. The forces due to the braking torque must be taken into account and the arrangement must be compatible With the available space bearing in mind the foregoing constructional requirements.

It has been seen that this last condition makes it advantageous to reverse the mounting of the elements A, A relative to the elements B, B and to invert the chambers having the air cushions of the elements A, A relative to the chambers of the elements B, B.

The kinematic linkage connection between the suppor ing elements and the suspended mass comprises for example two pairs of members 87, 63 disposed in the form of a V and whose apex is connected to the base of the supporting element A, A and whose opposite ends comprise elements 69, 7t articulated to the suspended mass for pivotal motion about axes xx, .r'x' which are :arallcl with the longitudinal axis of the vehicle. It is advantageous to arrange that the articulation 65 of the forward member have a slight flexibility and that the connection '77. between the two members also have a certain flexibility, afforded for example by the interposition of rubber joints.

At its upper part the piston 3 of the supporting element A or A is connected to the vehicle body 12 by an elastic joint 73 so as to take into account the variations in the inclination of the supporting element which constitutes one side of variable length of a triangulated system comprising the members 67, 68 and the vehicle body.

These variation in the inclinations require, on the one hand, a swivel connection 74 between the conduit 75 connecting the hydraulic damper 22 and pneumatic spring 1 to the upper part of the hollow iston 3 and, on the other hand a flexible joint 76 in the mounting of the damper 22 and the pneumatic chamber on the vehicle body.

With regard to forces due to braking, the brake plate 77 (FIG. 3) is rigid with the cylinder of the supporting element and, on braking, a large torque tends to swing the supporting element in a plane perpendicular to tiat of PEG. 3. As the piston 3 is held at its upper end by the vehicle body, the braking forces tend to bend the supporting elements and cause the piston to jam in its cylinder. To overcome this difficulty, the cylinder 5 is divided into two parts and consists of, on the one hand, a lower sleeve 52 carrying the jet 51 and the sealing ring 61 clampe between the lower end of this sleeve 52 and a cylinder 73 closed at its lower end, and, on the other hand, an upper sleeve 79 surrounding the system with a slight clearance but having at its ends bushings 8% and S1 of anti-friction material in which the piston 3 has a slide fit.

The sleeve 79 is fitted without clearance in the outer tubular body 82 of the supporting element whereas the lower sleeve 52 and the cylinder 78 are mounted to float therein owing to provision of a spherical bearing face of a flange 83 in the sleeve 52 (see FIG. 4) engaged with an anti-friction spherical faced bushing 34 in the body 82. The centre 0 of the spherical bearing face is located substantially in the middle of the sleeve 30. Sealing means 85 at the upper part of the body 8?. bears in a fluidtight manner against the piston 3. The inside of the body 32 communicates with the low pressure reservoir by way of the connection 31.

The stub axle 11, the steering arm 65 and the brake plate 77 are rigid with the tubular body 82 which can turn about the piston 3 owing to the fact that its base is 9 connected to the apex of the V-shaped member 67, 63 by a swivel bearing 86.

The torques exerted by the wheel R on the brake plate 77 while the vehicle is travelling tend to bend the supporting element and the piston 3 is liable to jam in the cylinder. This jamming is precluded by the fact that the sleeve 82 is allowed to pivot about the centre of the spherical connection between the parts 33 and 34 and conform, without opposing an excessive stress, to the bending deflections of the piston 3 between the bushings Sh and 81.

Although specific embodiments of the invention have been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. A vehicle pneumatic suspension of the type in which the opposite pneumatic supporting elements of piston and cylinder type which connect the opposite wheels of a transverse set of wheels to the sprung mass of the vehicle have their cylinders communicating with each other through balancing conduit means, said opposite wheels are interconnected by a mechanical anti-roll device and each cylinder has an escape orifice adapted to be masked by the corresponding piston in an inner position of the latter and unmasked in an outer position of the piston, said suspension comprising a low-pressure liquid reservoir and lowpressure conduit means putting the cylinders in communication with the reservoir by way of said escape orifices, a volumetric liquid pump having an outlet, high-pressure conduit means connected to said outlet and to each supporting element in such manner as to put the cylinder thereof in permanent communication with the liquid pump, and a restricted passageway in each high-pressure conduit means between said outlet and each cylinder, said restricted passageway comprising a thin wall extending across said high-pressure conduit means and having a calibrated orifice formed therethrough, the high-pressure conduit means of said opposite supporting elements constituting said balancing conduit means, whereby the liquid pumped by said pump flows through each highpressure conduit means and the restricted passageway therein to the cylinders and ordinarily maintains the pistons in a position of equilibrium relative to their cylinders whereas if the piston of one of said opposite supporting elements masks the corresponding escape orifice there occurs an increase in the static pressure in said one of the opposite supporting elements owing to the pressure drop in the passage of the whole of the liquid delivered to the pump through the restricted passageway in the high-pressure conduit means of the opposite supporting element, thereby creating an anti-tilt efiect which is supplementary to the anti-roll effect of said anti-roll device and controls the level of the vehicle.

2. A vehicle pneumatic suspension as claimed in claim 1, wherein said anti-roll device is a torsion bar supported by said sprung mass.

3. A vehicle pneumatic suspension as claimed in claim 1 comprising a body having a first bore communicating with the outlet of the liquid pump, a stop valve in said first bore, and a second and a third bore communicating with said first bore and, respectively with each of the highpressure conduit means of said cylinders, said thin wall, being arranged in said second and third bores, respectively.

4. A vehicle pneumatic suspension of the type in which the opposite pneumatic supporting elements of piston and cylinder type which connect the opposite wheels of a transverse set of wheels to the sprung mass of the vehicle have their cylinders communicating with each other through balancing conduit means, said opposite wheels are interconnected by a mechanical anti-roll device and each cylinder has an escape orifice adapted to be masked by the corresponding piston in an inner position of the latter and unmasked in an outer position of the piston, said suspension comprising a low-pressure liquid reservoir and low-pressure conduit means putting the cylinders in communication with the reservoir by way of said escape orifices, a volumetric liquid pump having an outlet, high-pressure conduit means connected to said outlet and to each supporting element in such manner as to put the cylinder thereof in permanent communication with the liquid pump, and a restricted passageway in each highpressure conduit means between said outlet and each cylinder, the high-pressure conduit means of said opposite supporting elements constituting said balancing conduit means, whereby the liquid pumped by said pump flows through each high-pressure conduit means and the restricted passageway therein to the cylinders and ordinarily maintains the pistons in a position of equilibrium relative to their cylinders whereas if the piston of one of said opposite supporting elements masks the corresponding escape orifice there occurs an increase in the static pressure in said one of the opposite supporting elements owing to the pressure drop in the passage of the whole of the liquid delivered to the pump through the restricted passageway in the high-pressure conduit means of the opposite supporting element, thereby creating an anti-tilt effect which is supplementary to the anti-roll efiect of said anti-roll device and controls the level of the vehicle, said set of wheels being the steering wheels of the vehicle, the pistons of said opposite supporting elements extending downwardly into the corresponding cylinders which latter have a kinematic connection to the unsuspended mass of the vehicle, and the pistons being hollow and connected to said suspended mass, said high-pressure conduit means communicating with the cylinders through the top of said hollow pistons and a branch connection being provided in the high-pressure conduit means of each hollow piston which connection a liquid damper puts in communication with the movable wall of variable capacity air chamber of the suspension so as to transmit the relative movements of the piston and cylinder to said r air chamber.

5. A vehicle pneumatic suspension as claimed in claim 4, wherein the cylinder of the supporting element of each steering wheel is composed of an upper member and a lower member which a spherical swivel joint interconnects, in two separate regions so as to permit a slight bending of the piston when subjected to braking or other stresses, and the lower member being mounted so as to float and be capable of assuming a direction corresponding to that of the lower end of the hollow piston, there being provided a tubular body supporting the axle of the steering wheel and the brake plate and enclosing said upper and lower members which are mounted therein in a liquidtight manner.

References Cited by the Examiner UNITED STATES PATENTS 1,861,821 7/32 Schaum 2672 FOREIGN PATENTS 280,547 5/28 Great Britain. 96,115 9/22 Switzerland.

A. HARRY LEVY, Primary Examiner.

LEO RI G am ner, 

1. A VEHICLE PNEUMATIC SUSPENSION OF THE TYPE IN WHICH THE OPPOSITE PNEUMATIC SUPPORTING ELEMENTS OF PISTON AND CYLINDER TYPE WHICH CONNECT THE OPPOSITE WHEELS OF A TRANSVERSE SET OF WHEELS TO THE SPRUNG MASS OF THE VEHICLE HAVE THEIR CYLINDERS COMMUNICATING WITH EACH OTHER THROUGH BALANCING CONDUIT MEANS, SAID OPPOSITE WHEELS ARE INTERCONNECTED BY A MECHANICAL ANTI-ROLL DEVICE AND EACH CYLINDER HAS AN ESCAPE ORIFICE ADAPTED TO BE MASKED BY THE CORRESPONDING PISTON IN AN INNER POSITION OF THE LATTER AND UNMASKED IN AN OUTER POSITION OF THE PISTON, SAID SUSPENSION COMPRISING A LOW-PRESSURE LIQUID RESERVOIR AND LOWPRESSURE CONDUIT MEANS PUTTING THE CYLINDERS IN COMMUNICATION WITH THE RESERVOIR BY WAY OF SAID ESCAPE ORIFICES, A VOLUMETRIC LIQUID PUMP HAVING AN OUTLET, HIGH-PRESSURE CONDUIT MEANS CONNECTED TO SAID OUTLET AND TO EACH SUPPORTING ELEMENT IN SUCH MANNER AS TO PUT THE CYLINDER THEREOF IN PERMANENT COMMUNICATION WITH THE LIQUID PUMP, AND A RESTRICTED PASSAGEWAY IN EACH HIGH-PRESSURE CONDUIT MEANS BETWEEN SAID OUTLET AND EACH CYLINDER, SAID RESTRICTED PASSAGEWAY COMPRISING A THIN WALL EXTENDING ACROSS SAID HIGH-PRESSURE CONDUIT MEANS AND HAVING A CALIBRATED ORIFICE FORMED THERETHROUGH, THE HIGH-PRESSURE CONDUIT MEANS OF SAID OPPOSITE SUPPORTING ELEMENTS CONSTITUTING SAID BALANCING CONDUIT MEANS, WHEREBY THE LIQUID PUMPED BY SAID PUMP FLOWS THROUGH EACH HIGHPRESSURE CONDUIT MEANS AND THE RESTRICTED PASSAGEWAY THEREIN TO THE CYLINDERS AND ORDINARILY MAINTAINS THE PISTONS IN A POSITION OF EQUILIBRIUM RELATIVE TO THEIR CYLINDERS WHEREAS IF THE PISTON OF ONE OF SAID OPPOSITE SUPPORTING ELEMENTS MASKS THE CORRESPONDING ESCAPE ORIFICE THERE OCCURS AN INCREASE IN THE STATIC PRESSURE IN SAID ONE OF THE OPPOSITE SUPPORTING ELEMENTS OWING TO THE PRESSURE DROP IN THE PASSAGE OF THE WHOLE OF THE LIQUID DELIVERED TO THE PUMP THROUGH THE RESTRICTED PASSAGEWAY IN THE HIGH-PRESSURE CONDUIT MEANS OF THE OPPOSITE SUPPORTING ELEMENT, THEREBY CREATING AN ANTI-TILT EFFECT WHICH IS SUPPLEMENTARY TO THE ANTI-ROLL EFFECT OF SAID ANTI-ROLL DEVICE AND CONTROLS THE LEVEL OF THE VEHICLE. 